1. Field of the Invention
This invention pertains to movable closures, more specifically to a pivot shoe for mounting on a sliding window sash and in a track, for supporting the window sash at a desired height by bearing a brake shoe against the track when the window is rotated away from the track on the pivot shoe, thereby temporarily locking the window at the desired height. The shoe is designed for ease of assembly and installation.
2. Description of the Prior Art
One popular pivot shoe design comprises a rotating barrel cam which cams axially, radially, or both, to force one or more elements of the pivot shoe against the track in which the shoe slides as it supports the sash on a keyed shaft about which the sash rotates as the keyed shaft rotates the barrel cam.
The element forced against the track provides frictional braking resistance against movement of the pivot shoe along the track. The element so forced may be a flexible wall of the pivot shoe, a surface of the barrel cam, or a brake shoe that is moved within the walls of the pivot shoe by the barrel cam.
It is the integrity of the three piece assembly of the latter design, with which we are concerned. For example, in the prior art locking pivot shoe 24 shown in FIGS. 1-4, brake shoe 28, and barrel cam 30 together can fall out of opening 26 which is through body 40, when the barrel cam is set at 0 degree position 52 of body opening 26.
Retainer tab 46 at the front of the barrel cam keeps the assembly in the body when the barrel cam is rotated away from the 0 degree position 52 of body opening 26, except at 90 degree position 58 on opening 26, or at the 270 degree position, at which although the barrel cam is held in opening 26, brake shoe 28 can fall out of the opening.
In U.S. Pat. No. 4,610,108 patented Sep. 9, 1986 by G. Marshik, a locking pivot shoe has a barrel cam which forces serrated end portions of a U-shaped spring radially out into the track. The front of the barrel cam has a radial tab (36) which is received through a radial slot at the 0 degree position in the pivot shoe body opening so that the tab retains the barrel cam in the body at all positions other than that of the slot.
In U.S. Pat. No. 4,718,194, patented Jan. 12, 1988 by FitzGibbon et al., the barrel cam of the pivot shoe has a collar at the front and a radial tab at the back. The barrel cam is inserted at the front of the pivot shoe into an opening in the pivot shoe body. The tab passes through a vertical slot at the 0 degree position of the opening. The tab holds the barrel cam in the body at all positions but for the 0 degree position.
In U.S. Pat. No. 4,683,676, patented by Sterner, Jr. on Aug. 4, 1987, the barrel cam of the balance shoe has a retention lug or pin (62) which engages an annular slot in the body of the balance shoe except for a space between the right and left side of the split body at the 0 degree position of the opening formed in the body by the Left and right sides for receiving the barrel cam. The retention lug holds the barrel cam in the body for all positions but the 0 degree position.
In U.S. Pat. No. 4,590,708 patented by Campodonico on May 27, 1986, the barrel cam which slides into an opening in the pivot shoe has an annular groove that receives a bulge or pin (48) extending inwardly from the inner diameter of the opening. The pin and groove arrangement assures that the barrel cam does not unduly move axially out of the opening but for two rotational positions of the barrel cam when the groove clears the pin.
In U.S. Pat. No. 4,958,462 patented by Cross on Sep. 25, 1990, the barrel cam is prevented from forward exiting the opening in the barrel cam body by annular axial cam faces which engage mating axial cam faces in the body surrounding the opening. The barrel cam is prevented from rearward exiting the opening by a brake shoe which is driven by the rear end face of the barrel cam as the barrel cam is driven axially by the mating annular axial cam faces. The brake shoe has forward extending legs which snap into holes in the body within the opening, and thereby retains the barrel cam in the body by way of the contact with the rear end face of the barrel cam.
It is an object of the present invention to provide a locking pivot shoe which stays an integral unit after assembly of the camming elements and brake shoe in the pivot shoe body regardless of the rotary position of the barrel cam.
It is another object of the invention to provide a locking pivot shoe in which the brake shoe contributes to the long time integrity of the assembled unit.
It is another object of the invention to provide a locking pivot shoe which snaps into integral assembly without having to rotate the barrel cam to a new position after the barrel cam is fully inserted.
It is another object in the locking pivot shoe that the brake can be assembled on to the barrel cam by axial movement regardless of the rotatory position of the barrel cam.
It is another object of the invention that the brake is driven by direct camming action between the barrel cam and the brake.
It is still another object that the barrel cam, when at the 0 degree slotted position, be held in the locking pivot shoe body by the brake.
Another object of the invention is that the brake be held in the body opening by a partial axial interference fit between the brake and a wall of the opening.
A further object is that the above partial axial interference fit be between a protuberance and end wall of an axial groove for receiving the protuberance.
Other objects and advantages of the invention will become apparent to persons skilled in the art from the ensuing description.
Briefly, a locking pivot shoe body includes an opening through the body from the front of the body to the back of the body. A rotary barrel cam is mounted in the opening for rotation on an axis which passes through the front and the back of the body with the front of the barrel cam being toward the front of the body.
A brake shoe is mounted on the body for axial movement within the opening. The brake shoe is adapted for engaging the barrel cam for being urged by the barrel cam for the axial movement.
Means on the body for holding the brake shoe in the opening comprises an interference fit between the brake shoe and the inner facing surface of the wall of the opening, by a radial protuberance and an axially oriented groove for receiving the protuberance.
In one arrangement of the invention, the protuberance is on the inner facing surface of the opening wall, and the groove is on the brake shoe. The groove is open toward the rear of the brake, and includes a radial wall toward the front end of the brake shoe for engaging the protuberance and for limiting rearward excursion of the brake shoe.